新型轻质雷达吸波材料的应用研究及进展

综述了目前国内外轻质雷达吸波材料的研究动态,详细介绍了具有发展前景的空心微珠吸波材料、碳纳米管吸波材料、导电高聚物吸波材料、纳米吸波材料和智能隐身材料等新型轻质雷达吸波材料的隐身机理及最新研究状况,并对雷达隐身材料应用技术的未来做了展望.     

吸波材料的研究进展

主要阐述了隐身材料研究的重要性,综述了其研究现状并重点介绍了碳纳米管吸波材料、碳纤维吸波材料、SiC纤维吸波材料以及等离子体吸波材料,简要概述了其它吸波材料的研究进展,最后展望了隐身材料的发展方向。     

铁氧体复合吸波材料研究新进展

简要阐述了隐身材料的研究热点,重点介绍了铁氧体吸波材料及其复合吸波材料的最新研究进展,总结了铁氧体复合吸波材料在制备及应用过程中存在的主要问题,并对发展趋势进行了展望.     

吸波材料的研究现状与进展

吸波材料是一种重要的军用隐身材料，本文从主要吸波材料在军事领域应用出发，介绍了吸波材料的工作原理，分别论述了铁氧体吸波材料、金属微粉吸波材料、导电高聚物吸波材料、多晶铁纤维吸波材料及纳米吸波材料的研究现状和发展趋势，较为详细的介绍了高温吸波材料的性质和在吸波方面的机理、应用，并对其他新型吸波材料的研究现状也有论述。最后对吸波材料的应用前景进行了展望。     

纳米隐身复合材料的研究进展

介绍了纳米隐身材料的吸波机理，并重点回顾了国内外吸波材料的研究现状。最后提出了吸波材料的发展方向。     

雷达吸波材料在军品隐身防护包装中的应用探讨

分析了当代军品包装中隐身防护的重要性,介绍了目前在隐身包装中占据主导地位的雷达吸波材料(RAM)的机理和主要技术种类,并对涂覆型吸波材料的制备方法和国内外的研究进展进行了综述,认为未来军品隐身包装防护材料应具有防雷达、光学、热红外侦察等多频谱且智能化综合隐身性能。     

碳纳米管在聚合物基吸波隐身复合材料上的应用

针对新一代吸波隐身材料要求吸收强、宽频带、质量轻、厚度薄、功能多、红外微波吸收兼容以及具有优良的其他综合性能的要求,利用碳纳米管(CNTs)特殊的电磁吸波特性,以及聚合物优良的材料性能,研究开发碳纳米管聚合物基复合吸波功能材料是实现该技术的有效途径.从吸波材料的隐身机理出发,阐述了碳纳米管的电磁吸波特性,着重介绍了碳纳米管聚合物基吸波隐身复合材料的最新研究进展,并提出了该类材料今后发展着重应解决的技术问题.     

聚苯胺吸波材料的研究趋势及应用前景

随着隐身与反隐身技术的发展,电磁波吸收材料是当前功能材料领域的研究热点之一。本文简要叙述了聚苯胺在在雷达波智能隐身、红外智能隐身、可见光智能隐身方面的应用情况,指出聚苯胺吸波材料在智能隐身领域的良好发展前景,及其作为智能隐身材料实用化应注意的问题。综述了近几年来国内外有关功能质子酸掺杂聚苯胺、聚苯胺/无机、聚苯胺/聚合物复合吸波材料的研究现状,并展望了其应用前景。     

涂覆型雷达/红外复合隐身材料研究现状

论述了纳米材料、掺杂半导体材料、空心导电微珠、导电高聚物、视黄基席夫碱盐、等离子体吸波涂料以及多层结构吸波涂层等几种新型涂覆型雷达/红外复合隐身材料的隐身机理和发展现状,并指出目前复合隐身材料研究中存在的问题及其发展趋势.     

雷达吸波材料的研究进展

根据电磁波在介质中的传播理论,详细地介绍了雷达吸波材料的吸波原理;综述了各种雷达吸波材料的特点、性能、应用现状以及发展趋势;列举了几种新型雷达吸波材料的吸波原理、吸波性能与应用现状;展望了雷达隐身材料的发展趋势。     

冷热枪状态下弹枪相互作用的热力耦合分析

为了研究在冷热枪状态下弹枪的相互作用,以某型自动步枪的铜被甲弹丸与枪管为研究对象,建立了其相互作用的热力耦合有限元模型,模型结合了考虑温度对摩擦因数影响的摩擦力子程序以及基于火药燃烧过程的内弹道载荷子程序,对弹丸温度变化及其在全枪管中的运动进行了数值仿真分析。结果表明:冷枪时,铜被甲弹丸表层升温在200℃左右;400℃及700℃的假设热枪状态下,刚完成挤进时铜被甲弹丸表层温度已经接近熔点,在膛内运动过程中表层铜材料剥落,枪管内膛会出现了"挂铜"现象;另外,热枪状态下弹丸在膛内的攻角变化明显大于冷枪状态下的攻角,不仅印证了热枪射击精度比冷枪射击精度差,也揭示了造成此现象的机理:由于高温下铜被甲圆柱部材料软化脱落,变形不规则,造成弹丸在膛内及出膛摆动增大。     

Transverse impact of a ball on a sphere with allowance for waves in the target

The transverse impact of a solid projectile on an elastic spherical shell with a pivoting contour support has been studied. Inside the contact zone, the projectile-target interaction is described by a solution of the standard system of equations. Outside the contact zone, the points of the shell are displaced and the shell is deformed due to propagation of a nonstationary wave front. A solution in this region is constructed using ray series with variable coefficients representing jumps of the time derivatives of the unknown functions on the wave surface of strong discontinuity. These coefficients are determined to within arbitrary constants using momentless equations of motion of the shell points. The constants are determined by matching two solutions at the contact zone boundary. Using the obtained analytical expressions and plotted dependences for the contact force and dynamic inflection, it is possible to judge on the influence of the shell structure design on the dynamic characteristics of impact interaction.     

Elastoplastic model of cylindrical projectile-plate interaction

Elastoplastic models of the transverse impact of a cylindrical solid projectile on an isotropic elastic Uflyand-Mindlin plate have been studied using numerical simulation methods. Displacements of the plate points outside the contact region are caused by a transverse shear wave propagating at a finite velocity. This wave is formed at the moment of impact and represents a surface of strong discontinuity. Behind the transverse wave front, the unknown dynamic quantities are represented in the form of single-term ray expansions. The local crumpling of the target material proceeds in a quasi-static manner and its dependence on the contact force is described using an elastoplastic model. The dependence of the contact force on the elastoplastic properties of a target plate at the site of impact and on the contact disk inertia has been considered.     

Separation and velocity dependence of the drag force applied to a rigid ovoid of Rankine nosed projectile penetrating an elastic–perfectly-plastic target

Yarin et al. have developed an analytical solution for normal penetration of a rigid projectile of the shape of an ovoid of Rankine into an incompressible elastic–perfectly-plastic target. Here, the closed form expressions from this solution are used to analyze separation and velocity dependence of the drag force applied to the projectile. It is shown that for penetration velocities V below a critical value V_s, the target material maintains full contact with the projectile's surface, the drag force is due solely to the resistance of plastic flow in the target and it is independent of the velocity V. For V equal to V_s the separation point jumps from the projectile's tail to a point closer to its tip. For increasing values of V the separation point moves even further towards the projectile's tip causing a strong dependence of the drag force on velocity. In contrast, results of the cavity expansion model applied to this problem indicate that separation cannot occur and that the drag force depends on velocity for all values of V. These results emphasize the importance of accurately modeling the flow field around the projectile.     

Nonlinear transient dynamic response of a blade subject to a pulsating load in a decaying centrifugal force field

This study is concerned with an analytical solution for the nonlinear transient dynamic response of a rotating blade in a gas turbine engine experiencing dynamic unbalance due to a blade-off scenario leading to rotor unbalance. As a consequence of rotor unbalance, the blade experiences a pulsating load at its tip due to contact with the casing and a decaying centrifugal force field due to the rotor deceleration. The governing equations of motion consider the blade as an elastic Timoshenko beam of varying thickness subject to changing rotational speeds. The analysis takes into account the variation in the thickness of the beam, the coupled axial and lateral displacements of the beam as a result of Coriolis component of acceleration, shear deformation, rotary inertia, and friction resulting from the contact between the blade and the casing. Our findings indicate that the thickness profile of the beam plays a significant role in the transient response. It further reveals that the decaying centrifugal force field leads to a dramatic change in the dynamic response and the resulting forces on the blade.     

Effect of in-bore gas on railgun performance

Acceleration of a projectile in a nonevacuated railgun bore produces a series of shock waves traveling through the gas in front of the projectile which retards the projectile's motion. A model is presented which describes the three components of this retarding force-the force required to accelerate the gas to the projectile velocity as it is entrained by the shock front, the force required to continue to accelerate previously shocked gas as the projectile accelerates, and the force required to overcome the viscous drag which arises from the interaction of the shocked gas and the gun tube. The authors address the relative contributions of the three components of the force and the significance of the retarding force when compared to the net accelerating force. The validity of the strong shock approximation for computing the retarding force is discussed     

锻造比对身管膛线成形影响分析

目的膛线是身管的关键部位,其主要作用是使弹头旋转运动,以保持弹头飞离膛口后稳定飞行。膛线成形性的状况对枪管的初速、精度都有重要的影响,故需要分析径向锻造过程中不同锻造比对身管膛线成形性的影响。方法使用有限元商业软件Abaqus建立三维有限元模型,对身管膛线的成形过程进行数值模拟,得出不同锻造比对身管膛线成形影响的规律。结果锻造比大于35%时,阴线的边界处的Mises应力大于材料的强度极限,膛线因应力过大而扭曲;锻造比小于15%时,阳线上的菱角处成形不充分,膛线的阴、阳线边界不分明;当锻造比为25%时,膛线应力分布在合理范围内且成形良好。结论通过仿真得出新材料的合理锻造比范围在25%左右,在15%~35%之间。     

Processing of Ceramic Rifled Gun Barrel

Ceramic gun barrels have the potential to provide a significant increase in barrel life as well as reduction in weight for small caliber systems. The potential use of ceramic tubes as gun barrels may be severely limited due to the difficulty in introducing the rifling on the inner diameter. The processing of ceramic gun barrels with internal rifling pattern poses a tremendous processing challenge to the materials community. The rifling lands and grooves and desired twist rate, coupled with the difficulty of machining ceramics, makes the economic manufacturing of such gun barrels extremely difficult. The current paper describes the preliminary efforts of fabricating an alumina gun barrel tube that was around 100-mm long with a 25-mm inner diameter (ID), a 33-mm outer diameter, and eight lands and eight grooves. Over and above the lands and grooves in the ID, the barrel had to have a 10:1 twist (one complete twist in 250-mm) incorporated into it. The paper will describes our preliminary attempts at processing such a rifled gun barrel tube made of alumina.